diff --git a/core/process.c b/core/process.c
index 7024366..d76a040 100644
--- a/core/process.c
+++ b/core/process.c
@@ -5,13 +5,14 @@
 #include "list.h"
 #include "mmuContext.h"
 #include "types.h"
+#include "thread.h"
 #include "uaddrspace.h"
 
 struct process {
     char name[PROCESS_NAME_MAX_LENGTH];
     int ref;
-    int pid;
-    int nextTid;
+    pid_t pid;
+    pid_t nextTid;
     struct uAddrSpace *addrSpace;
     struct thread *thList;
 
@@ -68,7 +69,7 @@ void processListPrint()
         struct thread *th;
         int nbTh;
 
-        printf("%d %s %d %d\n", proc->pid, proc->name, processCountThread(proc), proc->ref);
+        printf("%lu %s %d %d\n", proc->pid, proc->name, processCountThread(proc), proc->ref);
         list_foreach_named(proc->thList, th, nbTh, prevInProcess, nextInProcess)
         {
             if (th == cur) {
@@ -183,10 +184,10 @@ int processInitHeap(struct process *proc, uaddr_t lastUserAddr){
     return uAddrSpaceSetHeap(proc->addrSpace, lastUserAddr, 0);
 }
 
-int processGetId(struct process *proc){
+pid_t processGetId(struct process *proc){
     return proc->pid;
 }
 
-int processGetNextTid(struct process *proc){
+pid_t processGetNextTid(struct process *proc){
     return proc->nextTid++;
 }
diff --git a/core/process.h b/core/process.h
index 172aeb4..a28895f 100644
--- a/core/process.h
+++ b/core/process.h
@@ -1,9 +1,11 @@
 #pragma once
-#include "thread.h"
+#include "types.h"
 
 #define PROCESS_NAME_MAX_LENGTH 32
+typedef unsigned long int pid_t;
 
 struct process;
+struct thread;
 
 int processSetup();
 struct process *processCreate(char *name);
@@ -18,5 +20,5 @@ int processRemoveThread(struct thread *th);
 struct mmu_context *processGetMMUContext(struct process *th);
 struct uAddrSpace *processGetAddrSpace(struct process *proc);
 int processInitHeap(struct process *proc, uaddr_t lastUserAddr);
-int processGetId(struct process *proc);
-int processGetNextTid(struct process *proc);
+pid_t processGetId(struct process *proc);
+pid_t processGetNextTid(struct process *proc);
diff --git a/core/thread.c b/core/thread.c
index d450392..206bef8 100644
--- a/core/thread.c
+++ b/core/thread.c
@@ -14,7 +14,7 @@ static struct thread *currentThread;
 static struct thread *threadWithTimeout;
 static thread_id_t nextTid; // This is the TID for kernel thread ONLY
 
-thread_id_t threadGetId(struct thread *th)
+pid_t threadGetId(struct thread *th)
 {
     return th->tid;
 }
diff --git a/core/uaddrspace.h b/core/uaddrspace.h
index 9cf8cac..1456c4a 100644
--- a/core/uaddrspace.h
+++ b/core/uaddrspace.h
@@ -1,8 +1,9 @@
 #pragma once
 #include "mmuContext.h"
 #include "process.h"
+#include "stddef.h"
+#include "stdint.h"
 #include "types.h"
-#include <stddef.h>
 
 struct uAddrSpace;
 struct uAddrVirtualReg;
diff --git a/drivers/zero.c b/drivers/zero.c
index 4a830f3..b55bec3 100644
--- a/drivers/zero.c
+++ b/drivers/zero.c
@@ -3,6 +3,7 @@
 #include "alloc.h"
 #include "kernel.h"
 #include "klibc.h"
+#include "mem.h"
 
 struct zeroMappedEntry {
     int refCnt;
diff --git a/userspace/main_user.c b/userspace/main_user.c
index 92dc49b..3c5382b 100644
--- a/userspace/main_user.c
+++ b/userspace/main_user.c
@@ -123,7 +123,7 @@ int func_munmap()
 
 static void *print_hello(void *arg) {
         (void)arg;
-        printf("Hello World from thread %d\n", gettid());
+        printf("Hello World from thread %lu\n", gettid());
         usleep(100);
 
         return NULL;
diff --git a/userspace/unistd.h b/userspace/unistd.h
index e9675d3..db3d631 100644
--- a/userspace/unistd.h
+++ b/userspace/unistd.h
@@ -3,4 +3,4 @@
 typedef unsigned int useconds_t;
 int usleep(useconds_t usec);
 
-typedef int pid_t;
+typedef unsigned long int pid_t;